Physicochemical characterization of Escherichia coli:A comparison with gram-positive bacteria

Eight Escherichia coli strains were characterized by determining their adhesion to xylene, surface free energy, zeta potential, relative surface charge, and their chemical composition. The latter was done by applying X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR). No relationship between the adhesion to xylene and the water contact angles of these strains was found. Three strains had significantly lower surface free energies than the other strains. Surface free energies were either obtained from polar and dispersion parts or from Lifshitz-van der Waals and acid/base parts of the surface free energy. A correlation (r=0.97) between the polar parts and the electron-donor contributions to the acid/base part of the surface free energy was found. The zeta potentials of all strains, measured as a function of pH (2–11), were negative. Depending on the zeta potential as a function of pH, three groups were recognized among the strains tested. A relationship (r=0.84) was found between the acid/base component of the surface free energy and the zeta potential measured at pH=7.4. There was no correlation between results of XPS and IR studies. Data from the literature of XPS and IR studies of the gram-positive staphylococci and streptococci were compared with data from the gram-negativeE. coli used in this study. It appeared that in these three groups of bacteria, the polysaccharide content detected by IR corresponded well with the oxygen-to-carbon ratio detected by XPS

Low-risk susceptibility alleles in 40 human breast cancer cell lines

Background: Low-risk breast cancer susceptibility alleles or SNPs confer only modest breast cancer risks ranging from just over 1.0 to 1.3 fold. Yet, they are common among most populations and therefore are involved in the development of essentially all breast cancers. The mechanism by which the low-risk SNPs confer breast cancer risks is currently unclear. The breast cancer association consortium BCAC has hypothesized that the low-risk SNPs modulate expression levels of nearby located genes. Methods: Genotypes of five low-risk SNPs were determined for 40 human breast cancer cell lines, by direct sequencing of PCR-amplified genomic templates. We have analyzed expression of the four genes that are located nearby the low-risk SNPs, by using real-time RT-PCR and Human Exon microarrays. Results: The SNP genotypes and additional phenotypic data on the breast cancer cell lines are presented. We did not detect any effect of the SNP genotypes on expression levels of the nearby-located genes MAP3K1, FGFR2, TNRC9 and LSP1. Conclusion: The SNP genotypes provide a base line for functional studies in a well-characterized cohort of 40 human breast cancer cell lines. Our expression analyses suggest that a putative disease mechanism through gene expression modulation is not operative in breast cancer cell lines

Safe use of proton pump inhibitors in patients with cirrhosis

AimsProton pump inhibitors (PPIs) belong to the most frequently used drugs, also in patients with cirrhosis. PPIs are extensively metabolized by the liver, but practice guidance on prescribing in cirrhosis is lacking. We aim to develop practical guidance on the safe use of PPIs in patients with cirrhosis. MethodsA systematic literature search identified studies on the safety (i.e. adverse events) and pharmacokinetics of PPIs in cirrhotic patients. This evidence and data from the product information was reviewed by an expert panel who classified drugs as safe; no additional risks known; additional risks known; unsafe; or unknown. Guidance was aimed at the oral use of PPIs and categorized by the severity of cirrhosis, using the Child-Turcotte-Pugh (CTP) classification. ResultsA total of 69 studies were included. Esomeprazole, omeprazole and rabeprazole were classified as having no additional risks known'. A reduction in maximum dose of omeprazole and rabeprazole is recommended for CTP A and B patients. For patients with CTP C cirrhosis, the only PPI advised is esomeprazole at a maximum dosage of 20mg per day. Pantoprazole and lansoprazole were classified as unsafe because of 4- to 8-fold increased exposure. The use of PPIs in cirrhotic patients has been associated with the development of infections and hepatic encephalopathy and should be carefully considered. ConclusionsWe suggest using esomeprazole, omeprazole or rabeprazole in patients with CTP A or B cirrhosis and only esomeprazole in patients with CTP C. Pharmacokinetic changes are also important to consider when prescribing PPIs to vulnerable, cirrhotic patients

A leap towards unravelling the soil microbiome

As early as 1937, Franklin D. Roosevelt raised the importance of soil with his statement: “A nation that destroys its soil, destroys itself”. Soil is the groundwork of ecosystem functioning as it filters and stores freshwater, provides essential nutrients for plant growth, and regulates the earth’s temperature. Essential for this functioning is the abundance and diversity of the microbial life living in soil. However, as the majority of soil organisms are not culturable, for a long time it was impossible to identify all biota present in soil. Nowadays, using molecular markers (both DNA and RNA) as a proxy, it is possible to map soil communities much faster and in greater detail. Therefore, we have new opportunities to deepen our understanding of the soil microbiome in different contexts. One area of specific interest is the rhizosphere, soil in the direct vicinity of plant roots. Plants are able to influence the rhizosphere by releasing a broad range of carbon-containing substances in the soil, resulting in selection and boosting a subset of the soil living community. In this thesis the central aim was to explore to what extent plants are able to affect the rhizosphere food web to their own benefit under different circumstances. It was found that long term soil management practices are able to structurally change the soil microbiome but also plants are well capable of changing the local microbiome, to the extent that it exceeds the effect of management practices. Ahead of us lies the challenge to link soil biodiversity to soil function

Effect of nitrogen on fungal growth efficiency.

The contribution of fungi to carbon (C) and nitrogen (N) cycling is related to their growth efficiency (amount of biomass produced per unit of substrate utilized). The concentration and availability of N influence the activity and growth efficiency of saprotrophic fungi. When N is scarce in soils, fungi have to invest more energy to obtain soil N, which could result in lower growth efficiencies. Yet, the effect of N on the growth efficiencies of individual species of fungi in soil has not been studied extensively. In this study, we investigated the influence of different concentrations of mineral N on the growth efficiency of two common soil fungi, Trichoderma harzianum and Mucor hiemalis in a soil-like environment. We hypothesized that a higher N availability will coincide with higher biomass production and growth efficiency. We measured fungal biomass production and respiration fluxes in sand microcosms amended with cellobiose and mineral N at different C:N ratios. For both fungal species lower C:N ratios resulted in the highest biomass production as well as the highest growth efficiency. This may imply that when N is applied concurrently with a degradable C source, a higher amount of N will be temporarily immobilized into fungal biomass.</p

Effect of nitrogen on fungal growth efficiency

The contribution of fungi to carbon (C) and nitrogen (N) cycling is related to their growth efficiency (amount of biomass produced per unit of substrate utilized). The concentration and availability of N influences the activity and growth efficiency of saprotrophic fungi. When N is scarce in soils, fungi have to invest more energy to obtain soil N, which could result in lower growth efficiencies. Yet, the effect of N on growth efficiencies of individual species of fungi in soil has not been studied extensively. In this study we investigated the influence of different concentrations of mineral N on the growth efficiency of two common soil fungi, Trichoderma harzanium and Mucor hiemalis in a soil-like environment. We hypothesized that a higher N availability will coincide with higher biomass production and growth efficiency. To test this, we measured fungal biomass production as well as the respiration fluxes in sand microcosms amended with cellobiose and mineral N at different C:N ratios. We found that for both fungal species lower C:N ratios resulted in the highest biomass production as well as the highest growth efficiency. This may imply that when N is applied concurrently with a degradable C source, a higher amount of N will be temporarily immobilized into fungal biomass